1. Field of the Invention
The present invention relates generally to vehicle trailers and hitches, and more specifically to a hitch configuration which prevents rolling movement about the longitudinal axis of the hitch and trailer connected thereto. This permits the trailer to have only a single wheel for support, as two laterally disposed wheels are not needed to prevent roll about the longitudinal axis of the trailer. Various relatively light-duty trailers capable of carrying up to several hundred pounds of cargo are also disclosed herein.
2. Description of the Related Art
Vehicle trailers are almost universally provided with at least two laterally spaced wheels in order to provide lateral stability for the trailer. Further stability is provided by the hitch connection to the towing vehicle, thus defining three points of stability for the trailer (the two wheels and the hitch). This is sufficient to maintain the stability of the trailer while being towed.
As the trailer generally must articulate behind the towing vehicle (unless some relatively complex articulation is provided for the trailer wheels), a ball-type trailer hitch is generally used for most light to medium capacity trailers. Ball hitches are nearly universally available in various diameters, depending upon the internal diameter of the hitch ball receptacle on the trailer tongue. With the three degrees of angular freedom permitted, i.e., in pitch, yaw, and roll, ball hitches provide all of the articulation necessary between the towing vehicle and the trailer.
While articulation in yaw is required for the towing vehicle and trailer to negotiate turns, and at least some degree of pitch articulation is required to negotiate bumps and dips in the surface, the only need for articulation in roll, i.e., angular motion about the longitudinal axis between the trailer and towing vehicle, is due to the conventional two laterally spaced wheels used in nearly all small trailers. If the trailer did not require laterally spaced wheels, then it could roll about the same longitudinal axis as the towing vehicle. A single wheel would provide sufficient support for such a trailer. Such a single wheel trailer could be made narrower for more compact storage; wheel, tire, bearing, and (where provided) brake wear would be cut in half; and less rolling resistance would be encountered, thereby providing increases in fuel efficiency for the towing vehicle. Yet, these various advantages are not possible with a conventional ball-type hitch, or other hitch which allows rolling movement between the towing vehicle and the trailer.
The present invention provides a solution to this problem by means of a stabilizing hitch which permits only two degrees of freedom of motion between the trailer and towing vehicle, i.e., in yaw (for turning) and in pitch (for negotiating bumps and dips). The trailer tongue connected to the present hitch cannot rotate about the longitudinal axis of the assembly, but is locked relative to the roll axis of the towing vehicle. Thus, lateral stability of the trailer is provided by the hitch, rather than by laterally spaced wheels. This permits the trailer to be supported by only a single wheel, with all of the accompanying benefits noted above for such a single wheel trailer configuration.
The related art may be divided into two categories, depending upon whether the hitch allows the trailer to roll about its longitudinal axis relative to the tow vehicle and/or the trailer has at least two laterally spaced wheels, or whether the hitch restricts the roll about the longitudinal axis of the trailer and/or the trailer has only a single wheel for support. Those trailers and/or hitches which allow the trailer to roll about its longitudinal axis relative to the tow vehicle, and/or where the trailer has at least two laterally spaced wheels for support, are not felt to be particularly closely related to the present invention. Such trailers and/or hitches are described in the following U.S. and foreign patents and publications:
U.S. Pat. No. 2,635,892 issued on Apr. 21, 1953 to Russell Shutter, titled “Resilient Ball And Socket Type Draft Means;” U.S. Pat. No. 3,250,548 issued on May 10, 1966 to Barkley Boyd, titled “Trailer Hitch;” U.S. Pat. No. 3,700,053 issued on Oct. 24, 1972 to Wilmer E. Glissendorf, titled “Weight-Indicating Trailer Coupler;” U.S. Pat. No. 3,708,183 issued on Jan. 2, 1973 to Morris Jones, titled “Trailer Hitch;” U.S. Pat. No. 4,148,498 issued on Apr. 10, 1979 to Thomas A. Taylor, Jr., titled “Trailer Hitch; U.S. Pat. No. 4,215,876 issued on Aug. 5, 1980 to Donald E. Jacks, titled “Trailer Hitch;” U.S. Pat. No. 4,351,542 issued on Sep. 28, 1982 to Robert Lovell et al., titled “Flexible Towing Hitch;” U.S. Pat. No. 5,288,095 issued on Feb. 22, 1994 to Jackie J. Swindall, titled “Trailer Hitch;” U.S. Pat. No. 6,042,135 issued on Mar. 28, 2000 to Louis J. Ross, titled “Hitch Assembly And Trailer;” U.S. Pat. No. 6,357,778 issued on Mar. 19, 2002 to Louis J. Ross, titled “Hitch And Trailer Assembly;” and British Patent No. 1,140,551, published on Jan. 22, 1969, titled “Improvements In Or Relating To Hitches For Trailer Vehicles.”
None of the above-described devices has any means for preventing the lateral roll of the trailer about its longitudinal axis relative to the towing vehicle, as noted further above. However, the present inventor is aware of an additional number of references which describe means for preventing lateral roll of the trailer relative to the towing vehicle, and/or which provide only a single trailer wheel. These references are discussed individually below.
U.S. Pat. No. 1,048,951 issued on Dec. 31, 1912 to Darsie E. Edwards, titled “Pole Truck,” describes an elongate pole having a vertical shaft passing therethrough. A trailing arm having a single wheel extending therefrom is resiliently suspended on the shaft. While an eye is shown at the end of the pole behind the wheel, no forwardly disposed hitch is disclosed. The fact that the wheel swivels about its vertical attachment shaft would preclude any need for lateral articulation at the hitch attachment for the Edwards pole truck, whereas the trailer wheels of the present invention do not turn relative to the trailer and require a laterally articulating hitch.
U.S. Pat. No. 1,794,630 issued on Mar. 3, 1931 to Holman H. Linn, titled “Construction For Automobile Trailers And The Like,” describes a towing vehicle and trailer equipped with two laterally spaced ball hitches. The double hitch trailer attachment precludes movement of the trailer about the vertical (yaw) or longitudinal (roll) axes relative to the towing vehicle, and allows only pitching motion of the trailer. Thus, the single trailer wheel must swivel or pivot relative to the trailer in order to allow the trailer to turn behind the towing vehicle, without scrubbing the trailer tire sideways across the underlying surface. In contrast, the present hitch allows angular freedom of motion about both the pitch (lateral) and yaw (vertical) axes, while precluding motion about the roll (longitudinal) axis in order to require only a single, non-steerable trailer wheel.
U.S. Pat. No. 2,287,234 issued on Jun. 23, 1942 to Gilbert D. Ducharme, titled “Trailer Hitch,” describes a sliding pillar-type hitch, in which the trailer tongue attachment slides vertically on a post or pin attached to the towing vehicle. The tongue attachment is biased between a pair of springs for vertical suspension; no angular freedom of motion about the lateral or pitch axis is possible with this hitch configuration. While Ducharme also discloses a ball-type hitch in one embodiment of his hitch configuration, other embodiments would preclude motion about the roll axis of the trailer and towing vehicle. However, Ducharme does not disclose a single wheel trailer for use with his hitch, and none of his hitch configurations are structurally or functionally similar to the hitch of the present invention.
U.S. Pat. No. 2,486,605 issued on Nov. 1, 1949 to Reuel O. Ladd, titled “Axle Trailer Connector,” describes a complex pintle hitch assembly, in which the towing vehicle has a spring-loaded pin which passes through a ring on the trailer tongue. The relatively tight spacing of the trailer tongue ring between two plates on the pintle hitch precludes any significant movement about either the pitch or roll axes of the trailer; only yaw for turning is permitted. Accordingly, Ladd requires another articulated joint in the tongue structure of the trailer to allow the trailer to move in pitch relative to the towing vehicle. In any event, no single wheel trailer is disclosed by Ladd, and his hitch configuration is structurally and functionally different from the present hitch arrangement.
U.S. Pat. No. 2,523,733 issued on Sep. 26, 1950 to Leo L. Stephens, titled “Trailer Coupling Stabilizer,” describes a hitch assembly permitting only a single degree of arcuate motion about the pitch axis of the assembly. No yaw articulation is permitted; thus, a swiveling trailer wheel(s) similar to the wheel(s) of the Edwards '951 or Linn '630 U.S. patents, discussed further above, would be required for a trailer used with the Stephens hitch assembly. The present hitch permits arcuate motion about all but the roll or longitudinal axis of the trailer and towing vehicle, thus greatly simplifying the single wheel mechanism required for the trailer.
U.S. Pat. No. 2,558,153 issued on Jun. 26, 1951 to Frank O. Peterson, titled “One Wheel Collapsible Trailer,” describes a double hitch trailer assembly, generally similar to the double hitch trailer and towing vehicle assembly disclosed in the Linn '630 U.S. patent discussed further above. The Peterson hitches use laterally disposed pins which permit motion only about the pitch axis of the assembly, and require a swiveling wheel for trailer support. The present hitch assembly does not require any duplication of the hitch attach points on the towing vehicle, and may make use of the conventional single point hitch attachment (e.g., receiver type hitch, or ball hitch attachment plate, once the ball is removed) provided on the towing vehicle. Moreover, as the present hitch assembly permits the trailer to yaw freely behind the towing vehicle for turning maneuvers, the single wheel installation for the trailer is greatly simplified, as it need not swivel beneath the trailer.
U.S. Pat. No. 4,372,569 issued on Feb. 8, 1983 to Robert C. Otterson, titled “Single Wheel Trailer Support,” describes a trailing arm or castering wheel assembly having a pair of opposed springs acting in tension and compression to serve as the resilient suspension for the wheel. The entire assembly is attached to the trailer by a single vertically disposed bolt, to allow the wheel and suspension assembly to swivel beneath the trailer. Such a wheel assembly would be necessary with the hitches of the Linn '630, Stephens '733, and Peterson '153 U.S. patents, discussed further above, which do not permit the trailer to yaw behind the towing vehicle. However, the present invention does not require a swiveling wheel for the trailer, as the hitch permits the trailer to yaw or turn relative to the towing vehicle.
U.S. Pat. No. 4,484,759 issued on Nov. 27, 1984 to David J. Zwick, titled “Hitch Assembly For A Single Wheel Trailer,” describes a double hitch bar which is removably attachable to the rear bumper of a towing vehicle, for towing a single wheel trailer. A trailer attached to this hitch can articulate only in pitch about the lateral axis of the assembly; no yawing or turning motion is permitted. Accordingly, a swiveling trailer wheel is required for a trailer used with the Zwick hitch assembly. In contrast, the present hitch permits trailer movement about both the pitch and yaw axes but precludes motion about the roll axis, thereby permitting a single, directionally fixed wheel to be fitted to the trailer.
U.S. Pat. No. 5,368,325 issued on Nov. 29, 1994 to Donald B. Hazen, titled “Universal Single-Wheel Single Beam Trailer Having Adjustable Bed,” describes a double hitch configuration similar to the hitches of the Linn '630, Peterson '153, and Zwick '759 U.S. patents, each of which has been discussed further above. Such a laterally rigid hitch configuration requires a swiveling trailer support wheel or wheels similar to the swiveling trailer wheel of the Otterson '569 U.S. patent, rather than permitting the trailer to swivel relative to the towing vehicle, as in the present invention.
Finally, French Patent No. 2,608,547 published on Jun. 24, 1988, describes (according to the drawings and English abstract) a hitch for a light trailer, with the hitch having a pair of horizontally disposed plates which bear against one another to permit the trailer to yaw relative to the towing vehicle while precluding movement about the roll axis between trailer and towing vehicle. The trailer has a single directionally fixed wheel on a trailing arm suspension. However, the trailer suspension is quite complex in comparison to the trailer suspension of the present invention, and no resilient biasing of the trailer tongue to the hitch is provided. The present hitch assembly includes a spring assembly between the trailer tongue and the box in which it attaches, and moreover the present disclosure includes a variety of trailer configurations for different purposes.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. Thus, a single wheel trailer and stabilizing hitch solving the aforementioned problems is desired.